1. Field of the Invention
The present invention relates generally to semiconductor wafer preparation and, more particularly, to the cleaning and drying of a semiconductor substrate using space-and process efficient spin, rinse, and dry (SRD) modules.
2. Description of the Related Art
Wafer preparation and cleaning operations are performed in the fabrication of semiconductor devices. One common wafer preparation operation dispersely repeated during substrate preparation is a spin rinse and dry operation using a spin, rinse, and dry (SRD) module. Typically, the spin, rinse, and dry operations are performed in a bowl mounted on an SRD housing, which in turn is secured to a spindle. Typically, a motor causes the spindle, a chuck mounted on the spindle, and the wafer held by spindle fingers attached to the chuck to rotate. Generally, to receive the wafer to be prepared, the spindle fingers move upwardly within the bowl such that they extend outside the bowl and above the wafer processing plane. At this point, an end effector delivers the wafer to be processed to the spindle fingers. Subsequent to receiving the wafer, the spindle fingers and the wafer attached thereto move back down and into the bowl, thus placing the wafer at the level of wafer processing plane.
Generally, the wafer is rinsed by applying de-ionized (DI) water onto the surface of the wafer through a spigot, as the wafer is spun at high revolutions per minute (RPMs). Once the rinsing operation has concluded, the supplying of DI water is stopped by turning off the spigot, and then wafer is dried as the wafer is continuously spun at high RPMs. As soon as the drying operation has completed, for a second time, the chuck, the spindle fingers, and the wafer are moved out of the bowl and above the wafer process plane. At this time, an end effector reaches in and removes the wafer from the SRD module.
Several limitations are associated with the conventional SRD modules. Primarily, in the typical SRD modules, the wafers are processed in the horizontal orientation. Consequently, to achieve a wafer surface free of contaminants, the wafer must be spun for a significant period of time at high RPMs, thus increasing the spin, rinse, and dry cycle per wafer. As can be appreciated, this reduces the overall throughput of the SRD module.
A second limitation is the disposing of the heavy and large chuck assembly as well as the large motor required to drive the chuck assembly inside the SRD module. A third limitation is the use of an enormous frame support to accommodate the multiplicity of forces created by the spinning of the wafer at high RPMs for an extended period. As a combined effect of these two limitations, the conventional SRD modules have significantly large frames and frame supports, thus unnecessarily occupying a significantly large valuable clean room space.
Additionally, besides unnecessarily occupying valuable space, the chuck assemblies have extremely complex designs. For instance, the chuck assemblies are designed to rotate and move up and down within the bowl so as to receive or deliver the wafer. As a result, the movement of the chuck assembly within the bowl mandates that the chuck remain properly calibrated so that it comes to rest at the exact process level. In the situations the chuck is not aligned properly, the chuck assembly must be realigned. This process is very time consuming and labor intensive, and it requires that the SRD module be taken off-line for an extended period of time, thus reducing throughput.
In addition to needing realigned constantly, the chuck assemblies perform unnecessary movements to load and unload the wafers to and from the spindle fingers. By way of example, in conventional SRD modules, the loading of the wafer onto the spindle fingers involves four stages. First, to receive a wafer, the chuck and the spindles are moved out of the bowl, such that the spindles are positioned above the wafer process plane. As a result, to deliver the unprocessed wafer to the edges of the spindle fingers, the end effector holding the wafer is first moved horizontally over the bowl at a level that is above the horizontal plane of the spindle fingers (which are already in the up position). Thereafter, the end effector must move downwardly (while over the bowl) until the wafer reaches the level of the spindle finger at which point the spindle fingers can engage the wafer. Once the spindle fingers have engaged the wafer, the end effector relinquishes the wafer and thus physically delivering the unprocessed wafer to the spindle fingers. Finally, to pull out, the end effector is required to move slightly down and away from the wafer before moving horizontally away from over the bowl. Each of the up and down movements of the end effector is performed using the “Z” speed of the end effector, which in fact is a significantly low speed. As a result, in each spin, rinse, and dry cycle, a significant amount of time is spent merely to load and unload the wafer. Hence increasing the SRD cycle per wafer, which in turn reduces the overall throughput of the SRD module.
In view of the foregoing, a need therefore exists in the art for a spin, rinse, and dry module that occupies less clean room space and produces higher throughput while efficiently improves the spin, rinse, and dry operations performed on the surfaces of the substrates.